f9b1e711f0
The 'nodup' option forces fdescfs to return real vnode behind file
descriptor instead of the fdescfs fd vnode, on lookup. The end result
is that e.g. stat("/dev/fd/3") returns the stat data for the underlying
vnode, if any. Similarly, fchdir(2) works in the expected way.
For open(2), if applied over file descriptor opened with O_PATH, it
effectively re-open that vnode into normal file descriptor which has the
specified access mode, assuming the current vnode permissions allow it.
If the file descriptor does not reference vnode, the behavior is unchanged.
This is done by a mount option, because permission check on open(2) breaks
established fdescfs open semantic of dup(2)-ing the descriptor. So it
is not suitable for /dev/fd mount.
Tested by: Andrew Walker <awalker@ixsystems.com>
Reviewed by: markj
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D30140
245 lines
6.2 KiB
C
245 lines
6.2 KiB
C
/*-
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* SPDX-License-Identifier: BSD-3-Clause
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*
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* Copyright (c) 1992, 1993, 1995
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software donated to Berkeley by
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* Jan-Simon Pendry.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)fdesc_vfsops.c 8.4 (Berkeley) 1/21/94
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*
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* $FreeBSD$
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*/
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/*
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* /dev/fd Filesystem
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*/
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/filedesc.h>
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#include <sys/kernel.h>
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#include <sys/jail.h>
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#include <sys/lock.h>
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#include <sys/mutex.h>
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#include <sys/malloc.h>
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#include <sys/mount.h>
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#include <sys/proc.h>
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#include <sys/racct.h>
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#include <sys/resourcevar.h>
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#include <sys/vnode.h>
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#include <fs/fdescfs/fdesc.h>
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static MALLOC_DEFINE(M_FDESCMNT, "fdesc_mount", "FDESC mount structure");
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static vfs_cmount_t fdesc_cmount;
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static vfs_mount_t fdesc_mount;
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static vfs_unmount_t fdesc_unmount;
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static vfs_statfs_t fdesc_statfs;
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static vfs_root_t fdesc_root;
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/*
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* Compatibility shim for old mount(2) system call.
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*/
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int
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fdesc_cmount(struct mntarg *ma, void *data, uint64_t flags)
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{
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return kernel_mount(ma, flags);
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}
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/*
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* Mount the per-process file descriptors (/dev/fd)
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*/
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static int
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fdesc_mount(struct mount *mp)
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{
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struct fdescmount *fmp;
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struct vnode *rvp;
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int error;
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/*
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* Update is a no-op
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*/
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if (mp->mnt_flag & (MNT_UPDATE | MNT_ROOTFS))
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return (EOPNOTSUPP);
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fmp = malloc(sizeof(struct fdescmount),
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M_FDESCMNT, M_WAITOK); /* XXX */
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/*
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* We need to initialize a few bits of our local mount point struct to
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* avoid confusion in allocvp.
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*/
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mp->mnt_data = fmp;
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fmp->flags = 0;
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if (vfs_getopt(mp->mnt_optnew, "linrdlnk", NULL, NULL) == 0)
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fmp->flags |= FMNT_LINRDLNKF;
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if (vfs_getopt(mp->mnt_optnew, "nodup", NULL, NULL) == 0)
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fmp->flags |= FMNT_NODUP;
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error = fdesc_allocvp(Froot, -1, FD_ROOT, mp, &rvp);
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if (error) {
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free(fmp, M_FDESCMNT);
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mp->mnt_data = NULL;
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return (error);
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}
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VN_LOCK_ASHARE(rvp);
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rvp->v_type = VDIR;
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rvp->v_vflag |= VV_ROOT;
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fmp->f_root = rvp;
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VOP_UNLOCK(rvp);
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MNT_ILOCK(mp);
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/* XXX -- don't mark as local to work around fts() problems */
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/*mp->mnt_flag |= MNT_LOCAL;*/
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/*
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* Enable shared locking so that there is no contention on the root
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* vnode. Note only root vnode enables shared locking for itself,
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* so this end up being a nop for the rest.
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*/
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mp->mnt_kern_flag |= MNTK_LOOKUP_SHARED | MNTK_EXTENDED_SHARED;
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MNT_IUNLOCK(mp);
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vfs_getnewfsid(mp);
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vfs_mountedfrom(mp, "fdescfs");
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return (0);
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}
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static int
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fdesc_unmount(struct mount *mp, int mntflags)
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{
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struct fdescmount *fmp;
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int error, flags;
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flags = 0;
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fmp = mp->mnt_data;
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if (mntflags & MNT_FORCE) {
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/* The hash mutex protects the private mount flags. */
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mtx_lock(&fdesc_hashmtx);
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fmp->flags |= FMNT_UNMOUNTF;
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mtx_unlock(&fdesc_hashmtx);
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flags |= FORCECLOSE;
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}
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/*
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* Clear out buffer cache. I don't think we
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* ever get anything cached at this level at the
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* moment, but who knows...
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*
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* There is 1 extra root vnode reference corresponding
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* to f_root.
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*/
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if ((error = vflush(mp, 1, flags, curthread)) != 0)
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return (error);
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/*
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* Finally, throw away the fdescmount structure.
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*/
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mp->mnt_data = NULL;
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free(fmp, M_FDESCMNT);
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return (0);
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}
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static int
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fdesc_root(struct mount *mp, int flags, struct vnode **vpp)
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{
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struct vnode *vp;
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/*
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* Return locked reference to root.
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*/
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vp = VFSTOFDESC(mp)->f_root;
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vget(vp, flags | LK_RETRY);
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*vpp = vp;
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return (0);
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}
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static int
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fdesc_statfs(struct mount *mp, struct statfs *sbp)
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{
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struct thread *td;
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struct filedesc *fdp;
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int lim;
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int i;
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int last;
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int freefd;
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uint64_t limit;
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td = curthread;
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/*
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* Compute number of free file descriptors.
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* [ Strange results will ensue if the open file
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* limit is ever reduced below the current number
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* of open files... ]
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*/
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lim = lim_cur(td, RLIMIT_NOFILE);
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fdp = td->td_proc->p_fd;
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FILEDESC_SLOCK(fdp);
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limit = racct_get_limit(td->td_proc, RACCT_NOFILE);
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if (lim > limit)
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lim = limit;
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last = min(fdp->fd_nfiles, lim);
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freefd = 0;
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for (i = fdp->fd_freefile; i < last; i++)
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if (fdp->fd_ofiles[i].fde_file == NULL)
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freefd++;
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/*
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* Adjust for the fact that the fdesc array may not
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* have been fully allocated yet.
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*/
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if (fdp->fd_nfiles < lim)
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freefd += (lim - fdp->fd_nfiles);
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FILEDESC_SUNLOCK(fdp);
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sbp->f_flags = 0;
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sbp->f_bsize = DEV_BSIZE;
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sbp->f_iosize = DEV_BSIZE;
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sbp->f_blocks = 2; /* 1K to keep df happy */
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sbp->f_bfree = 0;
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sbp->f_bavail = 0;
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sbp->f_files = lim + 1; /* Allow for "." */
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sbp->f_ffree = freefd; /* See comments above */
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return (0);
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}
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static struct vfsops fdesc_vfsops = {
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.vfs_cmount = fdesc_cmount,
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.vfs_init = fdesc_init,
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.vfs_mount = fdesc_mount,
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.vfs_root = fdesc_root,
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.vfs_statfs = fdesc_statfs,
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.vfs_uninit = fdesc_uninit,
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.vfs_unmount = fdesc_unmount,
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};
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VFS_SET(fdesc_vfsops, fdescfs, VFCF_SYNTHETIC | VFCF_JAIL);
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